The Mechanical Modernization Of A Classical Icon (November 2000)
The year is 1922. Warren G. Harding becomes the first President of the United States to be heard on the radio. The movie of the year is D.W. Griffith's last epic, The Orphans of the Storm. Rebecca L. Felton of Georgia becomes the first woman to be seated in the United States Senate. The entrance to King Tut's tomb was discovered in Egypt by archaeologist Howard Carter. Prohibition of alcohol was in effect and the Roaring '20s were well underway. And General Motors Corporation occupies its new office building in the New Center area, just north of downtown Detroit.
The building was originally commissioned by William Durant, who was instrumental in the formation of General Motors; in fact, it was originally to be known as the Durant Building. The du Pont family had ousted Durant the year before, however, and the building was named the General Motors Building.
Durant had commissioned Detroit architect Albert Kahn in 1919 for a new central office for the burgeoning company, an assignment Kahn called "a rare privilege." The office was designed to meet the modern requirements of Roaring '20s office workers and was, relative to the traditional office building of the time, huge. With over 1.2 million sq ft; 1,800 offices; four miles of corridors; and 30 elevators, it was the second largest office building in the world when it was completed. Luxuries included a ballroom, a gymnasium, indoor swimming pools, a day hospital, a billiards room, barber shops, and clothiers.
The building's classical motif included spectacular vaulted ceilings running through the first-floor lobbies, with styles drawn from the Italian Renaissance. Thick pillars are solid marble, doors and trim are bronze, and the floor is inlaid patterns of marble. Above, the office levels were furnished with linoleum floors, plaster ceilings, and large elevator lobbies.
Kahn's design detailed a building 15 stories high. While many office buildings of the time were designed as a central court or an E design, the General Motors Building consists of an elongated central block, with four projecting wings in the front and back. This design was intended to allow ample sunlight and fresh air to the employees in each office. The outside fascia consists of mainly limestone with a steel skeleton, and of course, all those windows. The projecting office wings of the building developed from a central spine of elevator lobbies, toilet rooms, stairwells, and other centralized needs. The multitude of windows functionally provided outside air circulation and ample natural lighting to the spacious interiors.
Considered by many to be among Detroit's greatest architectural jewels, the building was listed as a National Historic Landmark and added to the National Register on June 2, 1978. But in late 1996, the auto giant announced it would purchase the Renaissance Center on the shores of the Detroit River and move its corporate offices to downtown Detroit under a massive consolidation plan. The future of the 1.2-million-sq-ft classic was now unknown.
New Tenant, Aggressive ScheduleWhen General Motors made the announcement that it would relocate its headquarters to the Renaissance Center, it left a large question mark looming above the General Motors Building's future. Proposed uses for the building included the conversion to a new City Hall, but most of these plans were considered too controversial or costly. In October of 1998, the present plan to renovate the building and convert it to a state office building was announced in October of 1998. As a result:
- The City of Detroit retains a large historic building that can anchor one of Detroit's fastest-growing commercial and residential neighborhoods - Detroit's New Center Area;
- The State of Michigan can now offer the public one-stop-shopping in Detroit for state services.
General Motors was scheduled to complete its exodus from the building by the fall of 2000. If the State of Michigan was to successfully begin moving workers into the building in the spring of 2001, the project team would face an aggressive schedule, including demolition work on upper floors while lower floors were still occupied by General Motors staff. This phase would be followed by demolition on lower levels while construction occurred on the upper floors. And finally, occupancy would be phased into the upper floors while construction worked down to the lower floors. Albert Kahn Associates, Inc., the firm founded in Detroit in 1895 by Albert Kahn, was named architect-engineer of record for the renovation project, valued at more than $100 million.
Such a tightly coordinated schedule requires the complete cooperation and efficiency of the space designers, engineers, construction manager, and of course, contractors and construction personnel. Each phase of the construction has a different set of players, requiring the construction manager's and the architect-engineer's constant attention to coordination and uniformity of design and construction between the different project phases.
Ragtime Design In The 21st CenturyThe General Motors Building was designed in the style of the post-WWI office, before the advent of the air conditioned office. Barely a decade before the building was commissioned, William Carrier had published his article on psychometric formulae to promote the use of air conditioning. And it would be almost another 40 years before the merger of the ASR and ASH gave existence to the present organization of ASHRAE.
The fully air conditioned office would not appear until the end of the decade. Windows provided ventilation, and radiators provided heat. Building enclosures were not tight, and air quality was truly not an issue since the buildings were provided with operable sashes. By design, more than 5,000 single pane, operable-sash windows put every worker near a window, providing ample light and ventilation.
From a life safety perspective, although fire protection was a concern in the 1920s, the numerous studies of the NFPA regarding exit distances, automatic sprinklers, egress paths, etc. had not been presented. The NFPA itself had only been in existence less than 25 years. Sprinklers were primarily intended for the protection of property, not life safety.
The classic building of this era was equipped with design features that met the technology of the time. The structure itself was solid and durable, but the mechanical systems required design, renovation, and infrastructure development to meet the design requirements of the 21st century.
Air ConditioningDesign intent of the system is to provide outside air to all areas and to meet the intent of ASHRAE Standard 62A. The outside air is monitored and ddc controlled at the units to a minimum of 20 cfm per person.
Each building floor of the main building is divided into four zones. Each zone is provided with a nominal 60-ton water-cooled DX air conditioning unit to serve its area of the floor. Outside air is supplied to these units by removing a window at each location and installing an outside air louver in its place. The air-handling units (ahu) were selected to ensure that they could fit into the building. Physical size restrictions and limitations included the freight elevator size and the corridor opening between the elevator shaft and the stairwell.
Water-side economizers are provided for all air conditioning units. Economizer operation will be controlled to maximize free cooling operation. The economizer is enabled whenever the entering water temperature to the unit is approximately 6°F less than the air temperature. The economizer control valve modulates in response to the cooling load sensed by the unit. Control valve operation will maintain full flow through the unit at all times, since the overall pumping system is constant volume.
Mechanical cooling will be enabled during economizer operation. If the economizer valve is driven to 95% open and the cooling load is still not satisfied, the unit's scroll compressors stage on to maintain the setpoint. To maximize energy savings, the economizer control valve will remain fully open until the differential between the entering water temperature and the entering air temperature falls below the setpoint.
Computer RoomsThe State of Michigan needed additional cooling for its computer and communications center. The IT staff of the owner required a humidity-controlled center, located approximately halfway up the building vertically to optimize the cabling, wiring, and IT installation. In general, the single-pane, operable-sash windows would not allow humidity-controlled units.
The solution was to provide a 4-ft corridor around the 7th floor wing housing the computer area. This allowed installation of a vapor barrier and provided the IT specialists with an additional level of security. With the addition of the vapor barrier, self-standing cooling units with humidity control could be provided inside the IT area. The condensers for these DX units were installed on the roof in an area adjacent to the cooling tower for the wing. Conditioned ventilation air is provided from the general building system, while the computer room cooling load and the humidification load is handled by the computer room units.
Cooling TowersIn the 1970s, General Motors started an ongoing renovation project which provided four sets of closed-circuit cooling water units (dry coolers) on the building roof with supply and return cooling water piping extending down the existing spacious stairwells. Valved connections at each floor were extended at each floor renovation to heat pump units above the ceiling. In addition to this function, these risers were fitted with valved outlets for automatic sprinkler piping. The risers were interconnected at the mezzanine level, and the fire pumps were connected to provide a tri-water system (heating, cooling, and fire protection).
These risers were retained in the new design and are utilized for supplying cooling water to the new air conditioning units at each floor. The dry coolers were removed and replaced with cooling towers selected at 1,870 gpm from 100° to 85° with 77° wb entering temperature. The existing pumps supplying the older units were retrofitted to work with the new cooling towers. Each bank of towers is supplied with a trio of pumps, retrofitted to 935 gpm each, providing one pump as standby at each tower location.
The pump system is constant-volume and is provided with a three-way diverting valve to maximize the efficiency of the system.
ControlsThe project included a digital control monitoring system to monitor operation of all new equipment and the status of the building's perimeter heating system. The limited space and budget dictated that this system be designed as a ddc system utilizing microprocessor controllers interconnected with twisted pair of shielded wiring. This application meshed nicely with many systems, but the decision was made in the name of schedule to use the Trane (La Crosse, WI) Tracer system, since Trane terminal boxes and air conditioning units had already been prepurchased from competitive bids.
This system interconnects all terminal boxes, and both the vav and the fan-powered units, with their respective air conditioning units through a twisted pair of plenum-rated shielded wiring. The system coordinates the operation of the air conditioning units and the terminal boxes while adjusting the intake of outside air to ensure compliance with design criteria and ASHRAE standards.
The system is connected through a digital interface panel to the cooling towers. Control is maintained on water temperature to afford efficient operation for the actual air conditioning units and free cooling when conditions are appropriate.
A single computer terminal is provided at the building manager's office to monitor and control each of the units and functions of the coordinated hvac system.
Steam, Waste/Vent, And Domestic Water Piping RepairsThe existing heating system is a low-pressure steam system, typically using a radiator at each window. The steam supply piping is provided from the central steam system from Detroit Edison, as is the case with many buildings in this area. The steam enters the building and rises to the piping space above the top floor of the building and distributes downward. The system was originally intended to operate as a vacuum return system, but through the years, time had taken its toll, making operation ineffective.
To operate the building in a more efficient manner by allowing the building operators to turn the steam off to particular wings, control valves had been installed at the high point of the system to the downward distribution risers. Although this effectively limited the use of the steam, these valves also trapped condensate when the steam cooled down at this upper level. New steam traps were installed to alleviate this problem.
Since the lowest level of the building, the basement, did not extend the full footprint of the building, the condensate piping had run underground to the outer wings from the building. This piping had deteriorated to the point where it could no longer be considered reliable. New piping was routed at the concourse level to allow system integrity to hold the desired vacuum. The numerous steam traps at the radiators were replaced - all 4,500 of them. The vacuum condensate pump was also replaced.
Site surveys indicated some areas where new steam piping had been routed to coils. With these modifications, the design team is confident the building heating system will operate efficiently and as the original designers had intended.
Waste/Vent And Domestic Water Piping RepairsTo measure the degree of renovations required to the piping systems, a corrosion consultant was engaged to review the condition and life expectancy of the systems. The priority for renovation was to replace portions of pipe systems that were currently leaking, or could leak immediately as indicated by serious pitting and thinning of pipe walls.
In addition, renovation was done to ensure that pressure for water and other services was not reduced to a point where it would not meet applicable industry standards at the enduse point of the system. Based on the results of the corrosion study, this criteria directed the renovations to include replacement of water supply risers, including pressure regulating valves for lower floors, and replacement of recirculating hot water systems and pumps. The water supply service to the building was found to be in good condition and was left alone, including the supply pumps.
Sprinklers, Risers, And DistributionToday, a modern office building of 16 floors cannot be built without automatic fire suppression. This building had many areas that had been sprinklered over the course of various renovations. Fire pumps were located in the basement and served most of the retail occupancies of the lower levels. However, the majority of the building remained unsprinklered. The renovation scope included full sprinklering of all areas of the building.
New standpipes were installed in each of the stairwells adjacent to the existing 10-in. tower water risers. Each of the standpipes were provided with hose valve connections at each floor, while the two interior standpipes were also utilized as combination standpipes with automatic sprinkler connections. When connected to the existing fire pumps in the basement of the building, this provides a system in accordance with all building codes.
Installation And ConstructionAn important scheduling concern for the project was the procurement and installation of the air conditioning units. The units were prepurchased by the owner to ensure delivery in accordance with the construction schedule. In many ways, installing the air conditioning units was a "ship-in-a-bottle" installation. Four units per floor needed to be stripped down, with discharge plenum and side panels removed, to even fit into the existing freight elevator. In addition, the fan motor needed to be removed to get the weight down to less than the rated capacity of the elevator with the installation workers in the elevator.
Once on the designated floor, the units needed to be reassembled and rolled down the corridors, to their final location. For the far wing, this is a distance of over 200 ft. Then they needed to be moved through the "pinch-point" of ductwork and piping for the wings that the units serve. This required rolling the units through the corridors prior to the installation of ductwork and piping to the wings.
In the end, the electrical and mechanical work within the wings was begun prior to the installation of the air conditioning units, but no connections between the wings could be made until after the units were in place.
The cooling water piping to the units is supplied from the adjacent stairwells. The rooms where the air conditioning units are installed are purposefully located adjacent to the stairwells. This minimizes the piping for the risers to the units and also minimizes interference with other systems.
Design ConstraintsUnlike modern office buildings that are designed for electrical and mechanical utilities, buildings of this vintage had little need for ceiling space to accommodate ductwork, automatic sprinklers, and communications cable trays. The plaster ceilings of these areas were located high and sometimes tight to the building structure above. The General Motors Building was of this type of construction.
In most areas, a plaster ceiling was originally installed at the bottom of the concrete beams of the floor above. The floor-to-floor spacing of the building was also substantially less than modern construction would provide. For most floors, this floor-to-floor height is only 12 ft at most floor levels. A similar use-type building in modern construction has approximately 18 to 30 in. more space between floors.
To accommodate this design constraint, mechanical systems needed to minimize the vertical depth of the ductwork and coordinate the design of the corresponding piping systems. For the General Motors Building, supply ductwork was constrained to 14 in. maximum depth. In addition, the use of return ductwork was limited to areas with acoustic or other special design concerns. Most areas utilize the space between the existing plaster ceiling and the new lay-in ceiling as plenum. The automatic sprinkler piping is installed as low as possible, at the same plane as the lighting fixtures. This requires more coordination between the terminal box, light fixture, and sprinkler system than might be normal, but it is required when working within the tight space conditions.
At the entrances to the building wings, the installation was a challenge for the design team. At these pinch points, the ductwork was installed first but needed to create passageways, sometimes even with notches in the sheet metal, to allow the passage of other mechanical system piping.
ASHRAE 62-89One design criterion that was present from the beginning of the project was to provide a safe and healthy building to the owner. To meet this criteria, ASHRAE Standard 62-89 was utilized for all outside airflows into the building. This did, however, create its own areas of problems.
With the size of the air conditioning units limited by space and budget, providing air to all areas of the building from these units became quite an obstacle. The nominal 60-ton units could easily become 20% larger if the ASHRAE 62-89 design criteria for conference rooms became the driver for the unit size. For although the supply air for the conference room could be designed for a design cooling day and provide an adequate amount of outside air, the same conference room would require the same amount of outside air even at reduced airflows to the room, and this condition would occur even at design heating days.
This increased percentage of outside air could drive the mixed-air temperature delivered to the space to less than 50° on design heating days and would increase the cooling capacity required at the unit during nonheating days. The effects of this single air supply source design snowballed quickly in analysis. Since the conference room areas became the driver for the percentage of outdoor air, it was decided to supplement the outside air to the conference rooms by using fan-powered, dual duct supply air terminal boxes. One supply would be conditioned 55° air from the air conditioning unit, while the other supply would be fresh air from a louver in the upper window of the conference room. This air is heated with an electric heating coil so that no air delivered to the space is less than 55°.
Although this design approach minimized the outside air requirement at the unit to approximately 30%, the total amount of outdoor air to the building is still significantly higher than normal pressurization would require. Since the units are located modularly at individual floors, there was no provision for return air fans or relief air at the units. Just as the building's window area was utilized to meet outside air requirements, the window space was used for building relief air. Small pressure-sensitive dampers are installed at the top of the windows to provide the relief area at approximately four per wing.
Working With The Existing BuildingThe top two floors of this building were the home to many of the General Motors corporate elite throughout the years. Of particular interest is the southeast corner of these top two floors. The Board of Directors meeting room was located at the very south end of the 15th floor, and the Chairman's office was located directly below it with a nearby stairwell specifically for the traffic between these rooms.
The historic significance of these rooms was quickly recognized, as was the opportunity to utilize these rooms with the State of Michigan as a client. The Board Room could be used as a meeting room with the Court of Appeals floor and the Chairman's office could be utilized as the governor's office when he was in town. These areas were therefore designated as historic areas not to be demolished and left "as-is," except that new hvac was to be provided. This presented the hvac design challenge of how to upgrade the existing systems without disturbing the stucco ceilings or solid wood paneling.
Both rooms were connected to the new air conditioning system units. The Governor's office, as it is now referred to, was originally air conditioned with perimeter fan-coil units in enclosures along with the perimeter heating coils. New ductwork was routed outside the office, and the office is provided with linear diffusers at the walls of the office so as to not disturb the ceiling. The linear diffusers will be cut into the wood paneling so as to blend with the existing surface.
The boardroom, being at the top floor, was provided with a custom rooftop ahu some 30 years ago. This unit box included supply and return air fans for the board room and an exhaust fan for an adjacent toilet room. This existing DX system was past useful life when reviewed, and it was decided to utilize the new system for this room also. New ductwork was extended from the new unit to near the boardroom. The ductwork was then extended through the roof and routed to the existing custom rooftop unit box. The box itself was gutted but used as an enclosure to connect the new and existing ductwork together. Thus, the ceiling of the existing boardroom was left undisturbed.
A Piece Of HistoryAt the printing of this article, construction is well underway with sheet metal and piping entering into the historic building. But the new era of the State of Michigan has arrived and the project proceeds on schedule. The design, program management, and construction team members continue to diligently work through the challenges inherent to a project of this magnitude.
The first state employees are scheduled to begin occupancy of this new office center for the State of Michigan in March 2001, with many others to follow throughout the year. By the end of 2001, the renovation construction will be complete. The State of Michigan will occupy a modernized, yet venerable, architectural piece of history, and plans to make it home for many years to come. For the State of Mighigan, Albert Kahn's classical masterpiece in Detroit should prove durable for yet another century. ES